Bottlebrush Shield Lichen

(Parmelia squarrosa)

Conservation Status
Bottlebrush Shield Lichen
Photo by Luciearl
  IUCN Red List

LC - Least Concern


NNR - Unranked


not listed


Bottlebrush Shield Lichen is a common, widespread, typical shield lichen. It occurs in Europe, Asia, and North America. In the United States, it occurs in the east from Maine to New Jersey, west to Ohio and Minnesota, and south along the Appalachian Mountains to northern Georgia. It also occurs on the West Coast from northern Washington to central California. In Minnesota it is relatively common in the northeast and north-central regions, but it is mostly absent from the remainder of the state.

Bottlebrush Shield Lichen is found in deciduous and mixed forests, both primary forests, undisturbed by human activity, and secondary forests, cleared by human activity and regenerated. It grows mostly on bark on the trunks, branches, and twigs of trees, including relatively young trees. It also grows on rocks, stones, and pebbles. It rarely grows on moss.

The vegetative body (thallus) is leaf-like (foliose), widely spreading, stretched out flat, and divided into overlapping lobes. The lobes are solid, 132 to 3 16 (1 to 5 mm) wide, elongated, and closely appressed to the substrate. The color may be bluish gray, greenish gray, or whitish gray. The upper surface may be flat or pitted. It often develops tiny cracks or breaks, allowing the inner white filaments (hyphae) to extend to the surface, appearing like tiny pores. These pores, called pseudocyphellae, often join together, forming a white, net-like pattern on the surface. Asexual reproductive structures (isidia) are produced on the margins and on the surface of the thallus. The isidia are cylindrical and up to 164 (.05 mm) tall. They are most dense in the central, older part of the thallus. Powdery reproductive granules (soredia) are not produced. The lower surface of the thallus is black. It is attached to the substrate by black, much branched, root-like structures (rhizines). The rhizine branches spread out at right angles (squarrose). This is the feature that gives the lichen its species epithet.

Reproductive structures (apothecia) may be present or absent. When present, they can be abundant. The apothecia are large, plate-like, and concave or flat. They may be pale and tan or yellowish tan, or medium and cinnamon brown.


Similar Species


Salted Shield Lichen (Parmelia saxatilis) rhizines are unbranched or forked.




Trees, rocks


Growth Form






Deciduous and mixed forests




Trees and rocks


Distribution Map



4, 24, 26, 29, 30, 81.





  Kingdom Fungi (fungi)  
  Subkingdom Dikarya  
  Phylum Ascomycota (sac fungi)  
  Subphylum Pezizomycotina  
  Class Lecanoromycetes (common lichens)  
  Subclass Lecanoromycetidae (shield lichens, sunburst lichens, rosette lichens, and allies)  


Lecanorales (shield lichens, rim lichens, and allies)  




Parmeliaceae (shield lichens and allies)  
  Subfamily Parmelioideae (typical shield lichens)  


Parmelia (shield lichens)  
  Mycobiont Parmelia squarrosa  

This lichen was previously described as Parmelia saxatilis. It was separated from that species in 1971 based on the distinctive right-angle (squarrose) branching of the rhizines. Molecular phylogenetic studies published in 2004 confirmed the separation.






Common Names


Bottlebrush Shield Lichen












An open, disk-shaped or cup-shaped, reproductive structure, with spore sacs on the upper surface, that produces spores for the fungal partner of a lichen. Plural: apothecia.



Adjective: Leaf-like growth form; referring to lichens with leaf-like growths divided into lobes.
Noun: The leaf-like, vegetative body of a lichen (thallus) that has thin, flat lobes which are free from the substrate.



A thread-like cell of a fungus that is the main mode of vegetative growth: the basic structural unit of a multicellular fungus. Plural: hyphae. Collectively, the hyphae of a fungus is the mycelium.



An asexual reproductive structure of a lichen in the form of a tiny outgrowth of the upper cortex. It consists of a cluster of algal cells (the photobiont) wrapped in fungal filaments (the mycobiont), and a shiny outer layer of protective tissue (cortex). Plural: isidia.



A root-like structure of a lichen that attaches the lower layer to the substrate.



An asexual reproductive structure of a lichen in the form of a tiny dull granule on the thallus surface that can be easily brushed off. It consists of a cluster of algal cells (the photobiont) wrapped in fungal filaments (the mycobiont), but without an outer layer of protective tissue (cortex). Plural: soredia.



In lichens: The vegetative body of a lichen composed of both the alga and the fungus. In liverworts: a flat, relatively undifferentiated plant body. Plural: thalli.





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    Bottlebrush Shield Lichen      








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January 2024

Location: Cass County

Bottlebrush Shield Lichen  






Created: 1/20/2024

Last Updated:

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